The proposal is for support of a comprehensive training program in the basic physiological state of the art techniques in membrane studies of epithelial transport. Specifically the aims of the project are to study the electrical characteristics of ion channels and electrogenic transport systems in epithelial cell membranes of the renal tubule. Methods introduced for the study of excitable tissue preparations and the measurements of single unit currents will be applied to epithelial cell membranes using the patch-clamp technique. The project will involve the analysis of apical channels and electrogenic transport systems in the luminal membrane of the proximal tubule. In addition, methods will be developed for the direct study of the basolateral membrane of the proximal tubule. Initial experiments will all be performed on cells of Ambystoma (salamander) kidney, a species with large cell size, thus allowing for comparison between patch-clamp measurements and classical electrophysiological measurements. In a second phase, these techniques will be extended to mammalian renal tubule preparations. The results of this project are expected to provide new information about transport systems which cannot be obtained with traditional single-cell impalements techniques used in electrophysiology of the kidney.